Ultra high frequency converter



Oct. 28, 1941. H. P. THOMAS 2,260,344

' ULTRA HIGH FREQUENCY oNvERTER Filed March l2, 1940 Figi.'

Inventor:

is Attorney.

Patented Uct. 28, 1941 UNITED s'rAres Parent OFFICE u Y I/JL'rRA HIGH General 4Electric Company, a corporation of New York Application March 1K2, 1940. seriai No. 323577 (o1. sst- 9 claims.

IThis invention relates to ultra-high frequency circuits for heterodyne conversion of ultra-high frequency waves into lower frequency waves for easier amplification and has for an object to provide a simple and easily -adjusted converter of such nature.

It is also an object of my invention to provide a converter circuit which includes a transmission line resonant to an ultra-high frequency Wave to be converted in frequency, and which also includes conversion means arranged in a simplified manner so that the heterodyne wave which produces the conversion is not short circuited by the resonant transmission line. v

The features of my invention which I believe' to be novel are set forth with particularity in the appended claims. My invention itself, however, both as to its o-rganizatio-n and method of operation, together with'further objects and advantages thereof may best be understood by reference to the following description taken in connection with the accompanying drawing in which Fig. 1 illustrates a circuit embodying my invention; Fig. 2 illustrates a .different form of circuit embodying my invention; and Fig. 3 illustrates a third modification 'of a circuit embodying my invention.

Referring to Fig. 1, an antennav I0 receives anv ultra-high frequency vwave inthe order of 30 to 50 centimeters in wave length and impresses it on aresonant or standing wave line II, I2, which is` terminated by a diode I3. A heterodyne oscillator I4 generates a wave which is also transmitted to the diode I3', where heterodyne action between the two waves produces a third wave as a modulation product, whose frequency is low enough to be readily amplified. This new wave is transmitted by suitable means, to be. described later, to an intermediate frequency amplifier and detector I5, which amplies and demodulates the wave, and then to an audio reproducer I6, which translates the audio wave produced by demodulai tion, into a sound wave.

Ina particular case,A wherethey diode I3 was a 955 tube with, the anode and grid connected together, the diode was found to be self-resonant at a wave length of about'l centimeters. Such self-resonance is due to internal capacitancebetween electrodes and to the inductance ofthe leads within the device and which comprise structural parts of the device itself. The end of the line II, I2 remote from the diode I3 is bridged by an adjustable connection I1 by which the line may be tuned. The antenna I0 is connectedv to the wire I I of the line through anadjustable tap'` fore preferred at present.

I8.' With such connections the line II, I`2 is adjusted to a length equal to one-half of a wave length ofthe wave received from the antenna I0, or to an inte'gralm'ultiple thereof, thereby to respon'd tol the wave received, which wave should anode and cathode when a current maximum' exists in its terminals;

The oscillator I4 transmits av wave to the diode I3 through a transformer I9, whose secondary Winding 20 impressesl theoutput ofy the oscillator through a condenser 2| upon the diode. The condenser 2l yis made of vsufficient capacitance to transmit Waves of the frequency generated by the oscillator I4 with low impedance. The frequency of the Wave produced by the oscillator I4 is chosen so that the line -I I, I2 has high impedance there# to. To satisfy this conditionfthe line must be an odd integral'multiple of a quarter Wave length ofv the wave from'the oscill-ator. The oscillator wave is rectified by thediode I3 and a harmonic therel of is produced across the electrodes of the diode. This harmonic heterodynes with the wave from the antenna I0 to produce the desired wave of intermediate frequency. When the length of line Il, I2 is equal to a half wave length of the wave receivedfrom the antenna, it is convenient to make the' oscillator .frequency different from but in the neighborhood of half the antenna frequency so that the second harmonic of the oscillator wave heterodynes to produce the intermediate frequency wave.

The line II, I2 does not affect the wave of fundamental frequency from the oscillator I4, if it is very nearly a quarter Wave, or an odd integral multiple thereof,`in length with respect thereto,4 so that a current maximum exists at the connection I1 and a voltage maximum at the diode I3. Similarly, the transformer I9 and the oscillator I4 present a higher impedance to the wave from the antenna I0 than the diode I3,` which is self-resonant at the frequency of the received waves, so that currents from the antenna I0 flow principally through the diode.

A condenser 22 is connected between the line II, I2, and the diode I3, and is of sufficient capacity to transmit a'wave from antenna' I0 vwith low impedance from the line II, I2 to the diode I3. The wave of intermediate frequency produced in the diode is made substantially lower in frequency than either of the waves from the oscillator I4 or from the antenna I0, so that the Condensers 2| and 22 can be and are given a suiciently high impedance to prevent the intermediate frequency wave from being short circuited by the oscillator I4 or the line II, I2 respectively. The intermediate frequency voltage therefore appears across both Condensers 2| and 22, and the amplifier I is connected across one of these Condensers, which may be, as is shown, condenser 2|. Such connection has been found to give excellent results when the line II, I2 has been tuned to waves between 35 and 40 centimeters long received by the antenna I 0.

Referring to Fig. 2, there is shown a slightly different connection of the amplifier I5 to be excited by the intermediate frequency wave from the diode I3. In this figure each part corresponds to a similar part shown in Fig. 1 and is given a like reference character. The amplifier I5, however, is connected in shunt to the diode I 3. This -amplier is provided with a higher impedance than the diode I3 at the frequency of either of the waves from the oscillator I4 or from the line II, I2, so that it does not absorb an appreciable amount of either of these waves.

It is to be noted that there is no short cir'- cuiting connection for the line II, I2 corresponding to the connection Il illustrated in Fig. 1. The frequency relations are somewhat different with this apparatus than with that of Fig. l, since line I I, I2 operates as an open ended standing wave line which is resonant only to waves which produce a voltage loop or po-int of maximum voltage upon the open end. For the wave received by the antenna I0, since a current maximum must exist at the terminals of the diode I3 in order that a voltage maximum for this wave shall exist between the anode and cathode thereof, the line II, I2 as in Fig. 1, must be resonant somewhere near the self-resonant frequency of the diode I3. The line II and I2 therefore may have an electrical lengthof one-quarter of a wave length of the wave received from the antenna I0, or an odd integral multiple thereof.

, In the apparatus illustrated in both Figs. 1

and 2 the physical length of the line II and I2 will usually not appear to be the same as the electrical length of the wave from the antenna I0 or of any multiple of one-quarter of that length. This is due to the fact that the apparatus can be operated in a considerable band near the self-resonant frequency of 'the diode I3. If it be operated below that freqdency, the diode I3 appears to have capacitive reactance and the mechanical length of the line II, I2 must be shorter than the apparent electrical length necessary. Correspondingly, if the line II, I2 be tuned to receive a Wave from the antenna III of higher frequency than the self-resonant frequency of the diode I3, the diode appears to be inductive, and the mechanical length of the line II, I2 appears somewhat longer than a multiple of one-quarter of the length of the wave from the antenna'III. I mean, therefore, when speaking of making the line II, I2 of a certain length in terms of Wave length, to indicate that the adjustment of the length of the line II, I2 shall be such that the apparatus as a whole is resonant to the wave referred to.

It is apparent that the oscillator I4 of Fig. 2 can be operated, as with Fig. 1, so that any harmonic of its wave which is produced in the diode I3 may heterodyne with the wave from the antenna I0 to produce the desired converted frequency. Two conditions are necessary in order that the converter operate properly in any case. The first condition is that the line II, I2 be adjusted in length to be resonant near the selfresonant frequency of the diode I3 and that the desired Wave from the antenna I0 be of the frequency to which the line II, I2 is resonant. So long as the frequency at which the oscillator I4 is operated is substantially different from the frequency of the wave received by the antenna I0, the diode I3 can be self-resonant thereto and a substantial part of the voltage from the oscillator I4 appears between the anode and cathode thereof. A second essential condition is that a frequency of operation of the oscillator I4 must be chosen so that a harmonic heterodynes with the antenna wave to produce the desired intermediate frequency wave and so that the line II, I2 offers a high impedance to the oscillator wave itself. For example, if the line II, I2 be made M of a wave length in length withrespect to the antenna wave, so that maximum current flows between the terminals of the diode I3 and maximum voltage exists between the open ends of the line II, I2, and if the oscillator be operated at 3/7 of the frequency of the Wave from the antenna, so that the line II, I2 is a half wave length with respect thereto, conversion can take place, an intermediate frequency being producedby heterodyne action between the third harmonic of the oscillator 4wave and the wave from the antenna so that a relatively lo-w intennediatefrequency appears.

Fig. 3 illustrates a dierent modification of my invention in which certain parts are similar to those shown in Fig. 1 and are given like reference characters. Instead of the diode I3, a triode 23 terminates the line II, I2, so that a control electrode 24 thereof is connected to wire I I and cathode 25 thereof to wire I2. The secondary 20 of the transformer I9 is connected directly betweenelectrode 24 and the cathode 25.

Condensers are unnecessary in this modification, since intermediate frequency voltage is not derived from the circuits to the antenna I0 and the oscillator I4, but this voltage is instead derived from the electron stream produced by the cathode25 and modulated by the electrode 24. An intermediate frequency amplifier, detector, and' audio reproducer 26 is connected between the cathode 25 and an anode 2'I of the discharge device 23 to amplify the intermediate frequency wave, detect it, and to reproduce the received signals.

The action of the circuits in this figure is similar to that of the apparatus shown by Fig. l. The impedance of the secondary 20 of the transformer I9 is made high compared to that of the path from the electrode 24 to the cathode 25 so that the wave from the antenna I0 is not absorbed by the transformer I 9. Similarly the line II, I2 has a length about one-half of a wave in length o-f the Wave from the oscillator I4, or some multiple thereof, so that a current maximum exists at the connection I1 and a voltage maximum exists between the electrode 24 and the cathode 25.

Itis obvious that my invention is not limited in scope to the exact circuits which are shown, since various modifications may be made such as using instead of the device I3 as shown, a diode having no control electrode therein connected as vdevice having more: than particularly in the typev of circuit shown in Fig. 3, in which the use. of screen and suppressor electrodes may be desired." Itis within the scope of my invention to use any sort of standing wave line. l I, l2, either open ended orv short-circuited as shown, and of any length which resonates withv a wave near the self-resonantfrequency of a converter discharge deviceand also'to use other harmonics thanvthe'second of the'wa've from the oscillator h1Y to be4 impressed across the converter device, so long as the oscillator wave is substantially different in frequency from the wave Vto lbe convertedA and is of such frequency as-to produce a voltagemaximum at the terminalsI of the converter device byresonance with `the line- Il, l2.v

WhileI have shown a particular embodiment of my invention, it will, of course, be understood thaty I do not wish to belimited thereto, since different modicationsmay be made both in the circuity arrangement and instrumentalities employed, and I aim by the appended claims to cover any such modifications asl fall within the true spirit and scope of my invention.

What I `claim as new and desire to secure by Letters Patent of the United States is:

1. In a heterodyne frequency conversion circuit,A an electron discharge device having a plurality'of electrodes, a source of an electric wave, a standing wave line terminated by two of said electrodes and energized by said wave from said source, said line being resonant to said wave, means operative at a lower frequency than said wave for utilizing said wave after conversion in frequency, means for impressing across said two electrodes a second wave of which a harmonic produces modulation products of said lower Irequency when heterodyned with said first wave in said device, said harmonic being related in frequency to said first wave so that said line presents a high impedance to said second wave, and means for transmitting said modulation products to said first means. l

2. In a heterodyne frequency conversion circuit, an electron discharge device having a plurality of electrodes, a source of an electric wave, a standing wave transmission line having la short circuiting device at one end `and two of said electrodes connected across its other end, said line being energized by the wave from said source and being adjusted so that said line terminated by said electrodes is resonant to said wave, an amplifier operative at a lower frequency than said wave, means for impressing across said two electrodes a second wave of which an even harmonic produces modulation products ofsaid lower frequency when heterodyned with said first wave in said device, said harmonic being related in frequency to said first wave so that said line presents a high impedance to said second Wave, and means for transmitting said modulation products to said amplifier.

3. In a heterodyne frequency conversion circuit, an electron discharge device having a plurality of electrodes, a source of an electric wave, a standing wave transmission line having one end open circuited and two of said electrodes connected across its other end, said line being energized by the wave from said source and being adjusted in length so that, when terminated by said electrodes, said line is resonant to said wave,

an'anode, orusing a one control electrode,

f an amplifier operative at a lower frequency than said wave, means for impressing across said two .a low frequency produces modulation-products of said lower frequency when heterodyned with said first wave in said device, saidharmonic being related in frequencygto4 said firstwave sof that said line presents a high impedanceto saidsecond wave, and means for transmitting said modulation products to said amplifler.

4'. In a heterodyne frequency conversion circuit, an' electron discharge devicey having two electrodes, andv terminals. and leads respectively connected thereto, saidel'ectrodes and leads being self-resonant at la certain frequency, a source of an electric wave whose frequency is nearrsaid certain frequency, a standing. wave transmission line connected across. said two terminals yat one end and. energized by the wave from said source, said line being resonant. to; said wave, an amplierfoperative at. al'ower frequencyl than said wave, means4 for impressing across said'two terminals a` second wave of which a harmonic produces modulation products of said` lower frequency whenheterodyned withsaid first. wave, said harmonic being related, in frequency to said first wave soA that. said line presents-al high impedance to saidr second wave, andmeans for transmitting saidV modulation products to said amplifier.

5. In, aheterodyne frequency conversion circuit, an electron ,discharge` device having a plurality of electrodes, a source ofan electric wave, a standing wave line terminated by two of said electrodes and energized by said wave from said source, said line being resonant to said wave, means operative at a lower frequency than said wave for utilizing said Wave after conversion in frequency, means for impressing across said two electrodes ia second wave of which a harmonic produces modulation products of said lower frequency when heterodyned with said first wave in said device, said harmonic being related in frequency to said first wave so that said line presents a high impedance to said second wave, means for preventing said line and said last means from short-circuiting vsaid modulation products, and means to transmit said modulation products from said short-circuit preventing means to said amplifier.

6. In a heterodyne frequency conversion circuit, an electron discharge device having a plurality of electrodes, a source of an electric wave. a standing wave line terminated by two of said electrodes and energized by said wave from said source, said line being resonant to said wave, means operative at a lower frequency than said wave for utilizing said wave after conversion in frequency, means for impressing across said two electrodes a second wave of whichr a harmonic produces modulation products of said lower frequency when heterodyned with said first wave in said device, said harmonic being related in frequency to said first wave so that said line presents a high impedance to said second wave, blocking condenser connected between said electrodes and said last means for preventing said line and said last means from short circuiting said modulation products, and means for transmitting said modulation products from said low frequency blocking condenser to said amplifier.

electrodes a second wave of which a harmonic '7. In a heterodyne frequency conversion circuit, an electrondischarge device having a plurality of electrodes, a source of an electric wave, a standing wave line terminated by two of said electrodes and energized by said wave from said source, said line being resonant to said wave, means operative at a lower frequency than said wave for utilizing said wave after conversion in frequency, means for impressing across said two electrodes a second wave of which a har-` monic produces modulation products ofsaid lower frequency when heterodyned with said first wave in said device, said harmonic being related in frequency to said first wave so that said line presents a high impedance to said second wave, means for preventing said line and said last means from short-circuiting said modulation products, and means for transmitting said modulation products from said discharge device to said amplifier. l

8. In a heterodyne frequency conversion circuit, an electron discharge device having a cath` ode, an anode, and a control electrode, a source of an electric wave, a standing wave line terminated by said cathode and control electrode Vand energized by said wave from said source, said line being resonant to said wave, means operative at a lower frequency than said wave for utilizing said wave after conversion infrequency, means for impressing across said cathode and control electrode a second wave of which a harmonic produces modulation products of said lower frequency when heterodyned with said rst wave in said device, said harmonic being related in frequency to said first wave so that said line presents a high impedance to said second wave,

and means connected between said anode and cathode including a source of potential for transmitting said modulation products to said first means.

9. In a heterodyne frequency conversion circuit, an electron discharge device having two electrodes and terminals and leads respectively connected thereto, said electrodes and leads being self-resonant at a certain frequency, a source of an electric wave whose frequency is near said certain frequency, a standing wave transmission line having a short circuiting device at one end and being connected across said two terminals at its other end, said line being energized by the wave from said source and being a half wave in length with respect thereto, an amplifier operative at a lower frequency than said wave, means for impressing across said two terminals a second wave whose second harmonic produces modulation products of said lower frequency when heterodyned with said rst wave, whereby said line presents a high impedance to said second wave, means for preventing said line and said last means from short circuiting said modulation products, and means to transmit said modulation products from said short circuit preventing means to said amplifier.

HENRY P. THOMAS. 

